Right now it crashes:

repl:4:> (def a-tab (new-Tab))
@Tab{:_meta @{:object-type :instance}}
repl:5:> (:new a-tab)
error: expected iterable type, got nil
  in new-from-Tab [repl] on line 3, column 1
  in _thunk [repl] (tailcall) on line 5, column 1